Evidence indicates that in CHF patients there is abnormal regulation of endothelium-dependent relaxing factor (EDRF-tentatively identified as nitric oxide or a derivative) and elevated circulating levels of endothelin (a vasoconstrictor). The purpose of this research is to characterize plasma EDRF and endothelin levels in patients with CHF, and to determine whether angiotensin plays a role in modulating EDRF and endothelin in such patients.